Know – may Allah have mercy upon you – that the first duty Allah has obliged upon the son of Aadam is al-kufr bit-taaghout and belief in Allah. And the evidence [for this] is the saying of the Exalted: And verily, We have sent among every ummah a Messenger [proclaiming]: 'Worship Allah [Alone] and keep away from taaghout.' [EMQ an-Nahl, 16:36]

As for the explanation of al-kufr bit-taaghout, it is to believe that anything [or anyone] that is worshipped instead of Allah is falsehood, and [one must] desert it and detest it, and make tafkeer to its people [those who worship it, i.e. the disbelievers] and to take them as enemies.

As for the meaning of al-Eemaanu Billaah, it is to believe that Allah is the Worshipped Lord – exclusively besides anything else – and to be sincere in all types of 'ibaadah (worship) to Allah, and to nullify it [one's worship] to any other ma’bood (false god), and to love the people of ikhlaas [i.e. the Muslims] and to have alliance with them. And [al-Eemaanu Billaah entails] hating the people of shirk and taking them as enemies.

And this is the Millah (religion) of Ibraaheem, which only the fool renegades against, and it is [also] the uswah (best example) which Allah has informed us about through His saying: Indeed there has been an excellent example for you in Ibraaheem and those with him, when they said to their people: 'Verily, we are free from you and whatever you worship besides Allah, we have rejected you, and there has started between us and you, animosity and hatred forever, until you believe in Allah Alone.' [EMQ al-Mumtahanah, 60:4]